docs: def plot_magnitude_time_scatter(
          catalogue, plot_error=False, fmt_string='o', filename=None,
          figure_size=(8, 6), filetype='png', dpi=300, ax=None):
      """
      Creates a simple scatter plot of magnitude with time
  
      :param catalogue:
          Earthquake catalogue as instance of :class:
          openquake.hmtk.seismicity.catalogue.Catalogue
      :param bool plot_error:
          Choose to plot error bars (True) or not (False)
      :param str fmt_string:
          Symbology of plot
      """
      if ax is None:
          fig, ax = plt.subplots(figsize=figure_size)
      else:
          fig = ax.get_figure()
  
      dtime = catalogue.get_decimal_time()
      # pylint: disable=len-as-condition
      if len(catalogue.data['sigmaMagnitude']) == 0:
          print('Magnitude Error is missing - neglecting error bars!')
          plot_error = False
  
      if plot_error:
          ax.errorbar(dtime,
                      catalogue.data['magnitude'],
                      xerr=None,
                      yerr=catalogue.data['sigmaMagnitude'],
                      fmt=fmt_string)
      else:
          ax.plot(dtime, catalogue.data['magnitude'], fmt_string)
      ax.set_xlabel('Year')
      ax.set_ylabel('Magnitude')
      ax.set_title('Magnitude-Time Plot')
  
      _save_image(fig, filename, filetype, dpi)